Tolerant mothers: aggression does not explain solitary living in the bush Karoo rat.

Many mammal species are thought to adopt solitary living owing to mothers becoming intolerant of adult offspring and the occurrence of social intolerance between adults. However, field studies on how solitary mammals interact are rare. Here we show that solitary living can occur without social intolerance. Over 3 years, we recorded interactions between free-living bush Karoo rats (Otomys unisulcatus) and conducted dyadic encounter experiments between kin and non-kin female neighbours, both in a neutral test arena and in field intruder experiments. Social interactions were rare (230/2062 observations), and they were aggressive in only 34% of cases. In dyadic encounters, mothers interacted amicably with young offspring. Aggression between mothers and offspring was almost absent. This mother-offspring relationship remained amicable even after adult offspring had dispersed. Aggression between neighbouring adult females was low in neutral arena tests, independent of kinship and season. However, in the field, females reacted more aggressively towards non-kin than kin intruders, especially during the breeding season. Tolerance between mothers and adult offspring indicates that aggression is not the mechanism leading to dispersal and solitary living. We found a solitary social system characterized by social tolerance, suggesting that dispersal and lack of social attraction rather than aggression can lead to solitary living.

Cognitive flexibility in urban yellow mongooses, Cynictis penicillata.

Cognitive flexibility enables animals to alter their behaviour and respond appropriately to environmental changes. Such flexibility is important in urban settings where environmental changes occur rapidly and continually. We studied whether free-living, urban-dwelling yellow mongooses, Cynictis penicillata, in South Africa, are cognitively flexible in reversal learning and attention task experiments (n = 10). Reversal learning was conducted using two puzzle boxes that were distinct visually and spatially, each containing a preferred or non-preferred food type. Once mongooses learned which box contained the preferred food type, the food types were reversed. The mongooses successfully unlearned their previously learned response in favour of learning a new response, possibly through a win-stay, lose-shift strategy. Attention task experiments were conducted using one puzzle box surrounded by zero, one, two or three objects, introducing various levels of distraction while solving the task. The mongooses were distracted by two and three distractions but were able to solve the task despite the distractions by splitting their attention between the puzzle box task and remaining vigilant. However, those exposed to human residents more often were more vigilant. We provide the first evidence of cognitive flexibility in urban yellow mongooses, which enables them to modify their behaviour to urban environments.

Wild mice in an urbanized world: Effects of light at night under natural and laboratory conditions in the single-striped grass mouse (Lemniscomys rosalia).

Urbanization, and the accompanying artificial light at night (ALAN), can disrupt the activity of animals. Such disruptions at the base of a food web can ripple through the ecosystem. Most studies of ALAN are performed in the laboratory. Thus, we lack basic information about the circadian responses of animals under natural environmental conditions to fully evaluate the impact of ALAN. We studied the behaviour and activity of wild-caught, peri-urban single-striped grass mice (Lemniscomys rosalia) under a natural treatment and in a standard laboratory treatment, including dim light at night to mimic conditions that they could experience. The species exhibited predominantly crepuscular activity under all experimental treatments. It showed the highest level of activity under the natural treatment, whereas ALAN significantly suppressed its activity. Males were more active than females under all experimental treatments. The marked changes in activity under ALAN is of particular concern since global change in combination with urbanization can lead to a change in vegetation density and composition that will decrease the number of suitable microhabitats and expose small mammals to novel habitat changes. We suggest that the single-striped mice could become vulnerable because of urbanization, leading to impacts on its ecosystem broadly.

Behavioral responses of vervet monkey Chlorocebus pygerythrus infants in a novel fostering program.

Vervet monkeys (Chlorocebus pygerythrus) are considered pests by farmers and homeowners. Consequent attempts to exterminate problem adult vervet monkeys often result in orphaned young offspring, which are sometimes taken to wildlife rehabilitation centers. We assessed the success of a novel fostering program at the Vervet Monkey Foundation, South Africa. Nine orphaned vervet monkeys were fostered to adult conspecific females of existing troops at the Foundation. The fostering protocol focused on reducing the time orphans spent in human rearing and involved a stepwise process of integration. We recorded the behaviors of orphans, including their interactions with their foster mother, to assess the process of fostering. Fostering success was high (89%). Orphans maintained close association with the foster mother and had little or no socio-negative and abnormal behavior. Comparison with literature showed a similar high fostering success in another vervet monkey study, regardless of the period and level of human-caregiving, and it is apparent that the duration of human care is less important than the protocol used for fostering. Nonetheless, our study has conservation relevance for vervet monkey rehabilitation.

Cognitive performance is linked to survival in free-living African striped mice.

Cognition is shaped by evolution and is predicted to increase fitness. However, the link between cognition and fitness in free-living animals is unresolved. We studied the correlates of cognition and survival in a free-living rodent inhabiting an arid environment. We tested 143 striped mice (Rhabdomys pumilio) using a battery of cognitive tests, including: (i) an attention task, (ii) two problem-solving tasks, (iii) a learning and reversal learning task, and (iv) an inhibitory control task. We related cognitive performance with days of survival. Better problem-solving and inhibitory control performance were significant correlates of survival. Surviving males showed greater reversal learning which may be related to sex-specific behavioural and life-history characteristics. Specific cognitive traits and not a composite measure of general intelligence underpins fitness in this free-living rodent population, enhancing our understanding of the evolution of cognition in non-human animals.

The effects of antibiotics and illness on gut microbial composition in the fawn-footed mosaic-tailed rat (Melomys cervinipes).

The gut microbiota are critical for maintaining the health and physiological function of individuals. However, illness and treatment with antibiotics can disrupt bacterial community composition, the consequences of which are largely unknown in wild animals. In this study, we described and quantified the changes in bacterial community composition in response to illness and treatment with antibiotics in a native Australian rodent, the fawn-footed mosaic-tailed rat (Melomys cervinipes). We collected faecal samples during an undiagnosed illness outbreak in a captive colony of animals, and again at least one year later, and quantified the microbiome at each time point using 16s ribosomal rRNA gene sequencing. Gut bacterial composition was quantified at different taxonomic levels, up to family. Gut bacterial composition changed between time periods, indicating that illness, treatment with antibiotics, or a combination affects bacterial communities. While some bacterial groups increased in abundance, others decreased, suggesting differential effects and possible co-adapted and synergistic interactions. Our findings provide a greater understanding of the dynamic nature of the gut microbiome of a native Australian rodent species and provides insights into the management and ethical well-being of animals kept under captive conditions.

Harshness is not stress.

We must differentiate between stressful and harsh environments to understand animals' resilience to global change. Harshness is not stress. Stressful environments activate the physiological stress response to increase energy availability, while harsh environments inhibit the physiological stress response to save energy.

Long-Term Spatial Restriction Generates Deferred Limited Space Use in a Zoo-Housed Chimpanzee Group.

BACKGROUND: Appropriate space is considered paramount for good captive animal welfare. There has been a concerted effort by captive institutions, particularly zoos, to provide captive animals with relatively large, naturalistic enclosures which havehad demonstrated welfare benefits for animals. However, post-occupancy assessments of these enclosures tend to focus on short-term welfare-centredbehavioural effects or human perceptions of the enclosures and their effects and seldom consider spaceuse. We examined the space use of a group of eight captive chimpanzees 5 years after large-scale enclosure modification at the Johannesburg Zoo, South Africa. METHODS: Instantaneous scan sampling was used to record behaviour and location of each chimpanzee at 5 min intervals in the new enclosure. From these 6.8 h of data, space-use patterns and subgroup (two or more chimpanzees within 10 m of each other) spacing were considered relative to local environmental variables, social conditions and the location and size of the previous smaller enclosures in which they had been kept. RESULTS: Space use was heterogeneous, with some enclosure zones being used more than others, and 97.5% of subgroups restricted their spacing to the dimensions of the previous housing (10 m × 10 m). CONCLUSIONS: This pattern was not explained by individual behaviour, time of day, location, available space, weather, temperature or shade availability, inter-individual spacing or subgroup composition. We suggest the learned helplessness phenomenon may explain these observations and discuss the implications for both animal welfare and endangered species conservation.Regardless of the mechanism, we suggest that such effects could be avoided through the provision of large enclosures for captive animals.

Social recognition and short-term memory in two taxa of striped mouse with differing social systems.

The ability to distinguish between familiar and strange conspecifics is important in group-living animals and influences the types of interactions between conspecifics. Social systems differ in sister taxa of the striped mouse genus Rhabdomys originating from different environments. Xeric-adapted R. pumilio displays facultative group-living whereas the mesic-adapted R. d. chakae is solitary. We assessed social recognition and attraction to strangers in females of two populations each of R. pumilio and R. d. chakae by means of a social discrimination task. We used a three-chamber apparatus developed in an established protocol and measured the latency of test females to approach and the duration of their investigation of stimulus females. Differences in social recognition of and preference for unfamiliar conspecifics in group-living and solitary-living taxa occurred at the taxon-level, even though constituent populations occurring kilometers apart showed similar responses. Females differed in the latency (testing phase) and duration of investigation (familiarization and testing phases) inter-specifically but not intra-specifically. Female R. pumilio approached stimulus females faster than female R. d. chakae. Female R. pumilio also investigated stimulus females for longer, regardless of stimulus type compared to R. d. chakae, but both taxa spent more time investigating familiar females than novel females and approached the familiar females faster than novel females. Social recognition, short-term memory, and social preference do not appear to differ between closely related taxa and differences in behavior between the two taxa might be related to inherent personality and social proclivity.

Characteristics influencing local enhancement in free-living striped mice.

Social learning is widespread across species; however, we still know little about the impact of individual differences in behaviour on social transmission. We aimed to investigate factors influencing social learning in free-living Rhabdomys pumilio, a group-living, arid-adapted mouse. We studied 52 mice in a lid opening task in a field laboratory. We created observer-demonstrator dyads with demonstrators either opening lids or not. We measured success of observers to open lids, their attention and latency to open and time spent interacting with the device. We also considered influences of observer age, sex, group size and personality traits. Demonstrator success did not influence observer success, although attention towards the demonstrator did impact the observers' time spent with the device. Males were more successful than females and more active/explorative observers interacted with the device faster and for a longer time compared to less active/explorative counterparts. We found no influence of age and group size on mouse success. Striped mice appeared to use cues from other individuals to learn how to solve the task and it was influenced by sex and personality. Striped mice in this studied population may use local enhancement to acquire information socially.

Variation in brain volume in nine populations and three taxa of the African striped mouse Rhabdomys.

Brain size can vary between populations in different environments because of different selection pressures on behaviours, such as learning and memory, related to spatial, social and environmental differences. We investigated the variation in total and broad-scale regional brain size in the murid rodent genus Rhabdomys from different environments. We assessed taxon-, population- and sex-level differences in total and regional brain volume in three populations each of three taxa (arid-occurring Rhabdomys pumilio and mesic-occurring Rhabdomys dilectus chakae and R. d. dilectus) originating across southern Africa. We µCT-scanned crania obtained from museums in South Africa and used digital software to create endocasts and extract total endocranium and regional volumes: olfactory bulb, anterior cerebrum, posterior cerebrum, cerebellum volume and petrosal volume. Total endocranial volume scaled with basal skull length and all-region volumes scaled with total endocranial volume. We found taxon-, and population-level differences in total endocranial volume. Relative anterior and posterior cerebrum volume did not differ significantly between taxa or populations, but relative cerebellum volume was larger in arid populations than mesic populations. Relative olfactory bulb volume was larger in mesic R. dilectus than in the R. pumilio, but petrosal lobule volume was larger in R. pumilio populations than in R. dilectus. Males had larger total endocranial volumes than females. Drivers of larger total endocranial volumes in R. pumilio are not immediately clear from our results. Environmental seasonality of food availability, cognitive buffering and locomotion may all correlate with total endocranial volume size, whereas the influence of sociality cannot be excluded. The environment and degree of semi-arboreality are likely driving variation in cerebellum, olfactory bulb and petrosal lobule volumes.

Sociability, but not spatial memory, is correlated with regional brain volume variation in the striped mouse Rhabdomys spp.

Local environmental conditions associated with different geographic areas may elicit variations in behavioural responses in animals, leading to concomitant differences in functional brain region volumes. We investigated the behavioural correlates of hippocampus and amygdala volumes in three sister taxa of the murid rodent genus Rhabdomys, occurring in different environments. We used a Barnes maze to test spatial memory, dyadic encounters to test social behaviour, and histological brain sections to calculate hippocampus and amygdala volumes. Arid-occurring R. pumilio made fewer errors and had shorter latencies in locating the escape tunnel compared to moist grassland-occurring R. d. dilectus and R. d. chakae in two probe trials, 48 and 96 h after the last learning trial. R. pumilio was more amicable than the R. dilectus subspecies in intra-specific dyadic encounters. R. pumilio had larger hippocampus and amygdala volumes than the other species. Smaller amygdala volumes were correlated with longer latencies in females for probe trial 1, but males showed similar latencies regardless of taxon. Higher amicability scores were correlated with larger amygdala volumes in all taxa. Higher amicability scores were correlated with larger hippocampus volumes in R. pumilio and R. d. chakae but smaller hippocampus volumes in R. d. dilectus. Correlative relationships between spatial memory and amygdala volume appeared 48 h, but not 96 h, after the last learning trial. Local environmental conditions may influence spatial navigation, but social correlates drive regional brain size within cryptic striped mouse taxa.

Seasonal changes in problem-solving in wild African striped mice.

Innovative problem-solving ability is a predictor of whether animals can successfully cope with environmental changes. These environmental changes can test the limits of animals, for example when energy availability decreases seasonally and, hence, problem-solving performance decreases because less energy is available for cognitive processes. Here, we investigated: (1) how problem-solving performance changed between seasons that differed significantly in food availability; (2) whether these changes were related to environmentally induced physiological changes in blood glucose and ketone levels, indicators of energy availability; and (3) whether individual variation in problem-solving was related to sex differences. We studied 99 free-ranging African striped mice, Rhabdomys pumilio, in the Succulent Karoo, South Africa, 55 during the hot dry summer with low food availability and 44 during the cold wet winter with higher food availability. We measured their problem-solving abilities using a food extraction task and found no seasonal differences in problem-solving success. However, mice solved the problem faster in summer versus winter. In summer, food availability was reduced and blood ketones increased but there was no seasonal difference in blood glucose levels. There were no correlation between problem-solving performance and blood glucose or ketone levels. Overall, more males solved the task than females. It appears that in striped mice cognitive functions can be maintained under harsh environmental conditions.

Quantifying the nutritional and income loss caused by crop raiding in a rural African subsistence farming community in South Africa.

Globally, crop damage by wildlife contributes to food insecurity through the direct loss of food and income. We investigated the calories lost and the potential economic impact of crop raiding at subsistence homesteads abutting the Hluhluwe Game Reserve, and assessed mitigation measures to combat crop raiding. We quantified the seasonal loss of calories (kJ/g) of four common crops, namely, beetroot, common bean, maize, and spinach, and determined the seasonal potential income loss. We used a stratified sampling approach to sample the homesteads. We found that season, crop type and the interaction between season and crop type predicted relative calorie loss and potential income loss, with the highest income loss recorded for spinach in the dry season. Significant differences were found for the potential income loss for all crop types in the wet season, and for the interaction between the crop types (maize, spinach) and the wet season. Farm slope was also a significant predictor of the relative calorie loss. Crop raiding animals, crops raided and distance of farms from the reserve all had a significant effect on the choice of mitigation measures of farmers. The highest relative calorie loss was for maize during the dry season, which could affect the subsistence farmers by reducing their daily calorie intake. This has an impact on their food security, especially during the dry season. Moreover, the most preferred mitigation measure used by farmers can have opportunity costs. These results have important implications for food security policies and practices.

Seasonal variation in reversal learning reveals greater female cognitive flexibility in African striped mice.

Cognitive flexibility describes the ability of animals to alter cognitively mediated behaviour in response to changing situational demands, and can vary according to prevailing environemental conditions and individual caracteristics. In the present study, we investigated (1) how learning and reversal learning performance changes between seasons, and (2) how cognitive flexibility is related to sex in a free-living small mammal. We studied 107 African striped mice, Rhabdomys pumilio, in an arid semi-desert, 58 during the hot dry summer with low food availability, and 49 during the cold wet winter with higher food availability. We used an escape box task to test for learning and reversal learning performance. We found that learning and reversal learning efficiency varied seasonally by sex: females tested in summer were faster at solving both learning and reversal tasks than males tested in winter. Performance varied within sex: males tested in winter showed faster learning compared to males tested in summer. During reversal learning, females tested in summer were more efficient and solve the task faster compared to females tested in winter. We suggest that seasonal cognitive performance could be related to sex-specific behavioural characteristics of the species, resulting in adaptation for living in harsh environmental conditions.

Problem Solving in Animals: Proposal for an Ontogenetic Perspective.

Problem solving, the act of overcoming an obstacle to obtain an incentive, has been studied in a wide variety of taxa, and is often based on simple strategies such as trial-and-error learning, instead of higher-order cognitive processes, such as insight. There are large variations in problem solving abilities between species, populations and individuals, and this variation could arise due to differences in development, and other intrinsic (genetic, neuroendocrine and aging) and extrinsic (environmental) factors. However, experimental studies investigating the ontogeny of problem solving are lacking. Here, we provide a comprehensive review of problem solving from an ontogenetic perspective. The focus is to highlight aspects of problem solving that have been overlooked in the current literature, and highlight why developmental influences of problem-solving ability are particularly important avenues for future investigation. We argue that the ultimate outcome of solving a problem is underpinned by interacting cognitive, physiological and behavioural components, all of which are affected by ontogenetic factors. We emphasise that, due to the large number of confounding ontogenetic influences, an individual-centric approach is important for a full understanding of the development of problem solving.

The Development of Anxiety and Exploration in Two Species of the African Striped Mouse Rhabdomys.

Genes and the environment interact to produce complex, environmentally relevant behaviors. We tested whether the behavior of two sister species of striped mice originating from different habitats (semi-arid Rhabdomys pumilio and grassland R. bechuanae) are modulated by the early social rearing environment. We cross-fostered pups between the species, and at adulthood tested their exploratory behavior and anxiety in open field and novel object tests, and a plus maze. We expected that the early social rearing environment would alter the phenotype of both species. Regardless of treatment, R. bechuanae were more exploratory and slightly less anxious than R. pumilio. However, fostered individuals of both species showed no changes in exploratory and anxiety responses. Thus there may be a genetic influence on behavioral development, or the early rearing environments of R. pumilio and R. bechuanae are not sufficiently different to alter behavior.

Do alternative reproductive tactics predict problem-solving performance in African striped mice?

In changing environments, animals face unexpected problems to solve. Not all individuals in a population are equally able to solve new problems. It still remains unclear what factors (e.g. age and body condition) influence the propensity of problem solving. We investigated variation in problem-solving performance among males following alternative reproductive tactics (ARTs). We studied a free-ranging population of the African striped mouse (Rhabdomys pumilio). Adult male striped mice can employ 3 ARTs: (1) dominant group-living breeders, (2) philopatric living in their natal group, and (3) solitary-living roamers. ARTs in male striped mice reflect differences in competitiveness, sociality and physiology which could influence their problem-solving performance. We tested a total of 48 males in 2 years with two tasks: a string-pulling task to reach food and a door-opening task to reach the nest. Since male striped mice differ in personality traits independent of ARTs, we also measured activity, boldness and exploration. In addition, we assessed the association of body condition and age with problem solving. Problem solving was related the interaction of age and ARTs. The younger philopatrics had better performance in a food-extraction task whereas the older breeders were faster at solving the door-opening task. Individual differences in traits related to personality were significant correlates of problem-solving performance: pro-active mice (i.e. more active and explorative and bolder) performed better in both tasks. Finally, problem-solving performance was not consistent between the two tasks. Our study provides evidence of correlates of ARTs, age and personality on problem-solving abilities.

Environmental correlates of exploratory behavior and anxiety in three African striped mouse (Rhabdomys) taxa occurring in different habitats and contexts.

Species or populations are locally adapted to the environments they occupy because of different selection pressures. Our study considers behavioral differences in rodents originating from environments with different levels of overhead cover. We investigated exploratory behavior and anxiety in 4 populations of the African striped mouse Rhabdomys, in South Africa, from different environments: R. pumilio from a semi-desert; R. bechuanae and R. d. dilectus, which were sympatric in the central grasslands; and another allopatric R. d. dilectus occurred in the northern grasslands. We tested all individuals in 5 standard laboratory tests: light-dark, startle response, open field and novel object tests, and the plus maze. In a principle components analysis, R. pumilio and the central grassland R. dilectus grouped together, and R. bechuanae and the allopatric R. dilectus grouped together, but there was some overlap between populations. Univariate analyses showed population-level differences in exploration and anxiety. R. pumilio and the central R. d. dilectus were more exploratory and less anxious than R. bechuanae and the allopatric R. d. dilectus. The behavior of R. pumilio (more exploratory and less anxious) reflects the open environments it occupies in nature, whereas the allopatric R. d. dilectus and R. bechuanae were less exploratory and more anxious reflecting the closed habitats they occupy. The similarity between R. pumilio and the central R. d. dilectus cannot be explained by habitat and might be related to the effects of coexistence between central grassland R. d. dilectus and R. bechuanae, which may potentially alter the behavior of one or both species. (PsycInfo Database Record (c) 2021 APA, all rights reserved).